Noticed a change in your US traffic patterns recently? Aside from the President’s Day holiday weekend, it may be due to the latest algorithmic tweak from Google.

Earlier this week Google rolled out a change – nothing unusual about that, it’s constantly tweaking, but this one noticeably impacts 11.8% of search queries according to the company. When you consider Google gets around a half billion U.S. searches a day; it’s a huge number that have been affected.

The official Google blog says the algorithmic change is to help weed out sites that are “low-value add for users, copy content from other websites or sites that are just not very useful”.

As a result, Google says there will be better ranking for high-quality sites focusing on original, in-depth content, reports and analysis.

An important point to bear in mind is that the changes were launched in the U.S. only; however, Google plans to roll it out elsewhere in the future.

Danny Sullivan over at SearchEngineLand has dubbed the change the Google “Farmer” update. Danny says while Google hasn’t said it is officially targeting content farms, he’s reading between the lines given the search engine said it would be targeting those types of sites.

Danny defines a content farm (paraphrasing here) as a site that creates low quality content specifically tailored to popular searches, with little thought, resources and useful information gone into creating the articles.

So, now the dust has settled, did Google’s algorithmic tweak work – was the “Farmer” update a success in terms of weeding out such sites from top positions in search engine results pages? Take a look at this report from Sistrix based on one million keywords and you be the judge.